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refactoring dns, ripped out dns packet generating code, removing dependency on io

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This commit is contained in:
Bjorn Andersson 2007-01-28 05:10:19 +00:00
parent c10fa59bbb
commit e56074b42a
2 changed files with 87 additions and 72 deletions
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1
TODO
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@ -19,3 +19,4 @@ STUFF TO DO:
- More/better documentation (as always)
- Modify readname to take the actual size of the buffer to fill, and make sure it adds a '\0' at the end. Then clean up dns.c to match the changes.

158
src/dns.c
View file

@ -38,6 +38,9 @@
#include "encoding.h"
#include "read.h"
#define QR_QUERY 0
#define QR_ANSWER 1
// For FreeBSD
#ifndef MIN
#define MIN(a,b) ((a)<(b)?(a):(b))
@ -195,48 +198,92 @@ dns_send_version(int dns_fd, int version)
dns_write(dns_fd, ++pingid, data, 6, 'V');
}
int
dns_encode(char *buf, size_t buflen, struct query *q, int qr, char *data, size_t datalen)
{
HEADER *header;
short name;
char *p;
int len;
memset(buf, 0, buflen);
header = (HEADER*)buf;
header->id = htons(q->id);
header->qr = qr;
header->opcode = 0;
header->aa = (qr == QR_ANSWER);
header->tc = 0;
header->rd = (qr == QR_QUERY);
header->ra = 0;
p = buf + sizeof(HEADER);
switch (qr) {
case QR_ANSWER:
header->ancount = htons(1);
header->qdcount = htons(1);
name = 0xc000 | ((p - buf) & 0x3fff);
p += dns_encode_hostname(q->name, p, strlen(q->name));
putshort(&p, q->type);
putshort(&p, C_IN);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0);
/*
* XXX: This is jidder! This is used to detect if there's packets to be sent.
*/
q->id = 0;
putshort(&p, datalen);
putdata(&p, data, datalen);
break;
case QR_QUERY:
header->qdcount = htons(1);
header->arcount = htons(1);
p += dns_encode_hostname(data, p, datalen);
putshort(&p, q->type);
putshort(&p, C_IN);
// EDNS0
putbyte(&p, 0x00); //Root
putshort(&p, 0x0029); // OPT
putshort(&p, 0x1000); // Payload size: 4096
putshort(&p, 0x0000); // Higher bits/edns version
putshort(&p, 0x8000); // Z
putshort(&p, 0x0000); // Data length
break;
default:
errx(1, "dns_encode: qr is wrong!!!");
/* NOTREACHED */
}
len = p - buf;
return len;
}
static void
dns_query(int fd, int id, char *host, int type)
{
char *p;
int len;
int peerlen;
char buf[1024];
HEADER *header;
struct query q;
int peerlen;
int len;
q.id = id;
q.type = type;
len = 0;
memset(buf, 0, sizeof(buf));
header = (HEADER*)buf;
header->id = htons(id);
header->qr = 0;
header->opcode = 0;
header->aa = 0;
header->tc = 0;
header->rd = 1;
header->ra = 0;
header->qdcount = htons(1);
header->arcount = htons(1);
p = buf + sizeof(HEADER);
p += dns_encode_hostname(host, p, strlen(host));
putshort(&p, type);
putshort(&p, C_IN);
// EDNS0
putbyte(&p, 0x00); //Root
putshort(&p, 0x0029); // OPT
putshort(&p, 0x1000); // Payload size: 4096
putshort(&p, 0x0000); // Higher bits/edns version
putshort(&p, 0x8000); // Z
putshort(&p, 0x0000); // Data length
len = dns_encode(buf, sizeof(buf), &q, QR_QUERY, host, strlen(host));
peerlen = sizeof(peer);
len = p - buf;
sendto(fd, buf, len, 0, (struct sockaddr*)&peer, peerlen);
}
@ -381,49 +428,15 @@ dns_encode_hostname(const char *host, char *buffer, int size)
return p - buffer;
}
void
dnsd_send(int fd, struct query *q, char *data, int datalen)
{
int len;
char *p;
char buf[64*1024];
short name;
HEADER *header;
int len;
memset(buf, 0, sizeof(buf));
len = 0;
header = (HEADER*)buf;
header->id = htons(q->id);
header->qr = 1;
header->opcode = 0;
header->aa = 1;
header->tc = 0;
header->rd = 0;
header->ra = 0;
header->qdcount = htons(1);
header->ancount = htons(1);
p = buf + sizeof(HEADER);
len = dns_encode(buf, sizeof(buf), q, QR_ANSWER, data, datalen);
name = 0xc000 | ((p - buf) & 0x3fff);
p += dns_encode_hostname(q->name, p, strlen(q->name));
putshort(&p, q->type);
putshort(&p, C_IN);
putshort(&p, name);
putshort(&p, q->type);
putshort(&p, C_IN);
putlong(&p, 0);
q->id = 0;
putshort(&p, datalen);
putdata(&p, data, datalen);
len = p - buf;
sendto(fd, buf, len, 0, (struct sockaddr*)&q->from, q->fromlen);
}
@ -494,3 +507,4 @@ dnsd_read(int fd, struct query *q, char *buf, int buflen)
return rv;
}